The present invention relates to a rebar retention device used in the construction industry, and to a method for using the device. More specifically, the invention relates to compressible retaining members associated with rigid members which are located within forms used in the placement and curing of concrete.
During the construction of structures utilizing concrete poured in situ, iron or wooden forms are provided and serve as a barrier and mold for the hardening concrete. Typically, cylindrical steel reinforcing bars ("rebar") are located within the concrete matrix and provide tensile strength to the concrete.
In paving operations, concrete roads or airstrips, for example, are constructed using large iron forms to enclose and shape the concrete matrix. Two basic methods have been used in the past to locate and position the rebar within the concrete. In one method, "gang drills," large drilling machines carrying multiple drills whose spacing and depth can be varied, have been used to drill holes at various locations through the still-hardening concrete pavement. Rebar can then be positioned in those holes. Since this drilling is a time-consuming and relatively expensive procedure, it is preferred to place the rebar before the concrete has been poured. In this, more typical, method, the forms themselves are used to support the rebar in position within the hardening concrete. It is this latter, preferred operation which is the subject of this invention.
When placing rebar in a location where wet concrete is to be poured for a paving operation, it is important that the rebar be positioned normal to the length-wise section of the form. As those of skill in the art will recognize, this will permit the rebar to strengthen the pavement in the most effective manner. This placement position is also important during form removal, which is typically accomplished by chaining the forms to a forklift or similar machine and forcing the forms in a horizontal direction to remove them from the concrete and rebar. It can be appreciated that if the rebar is not positioned so that it is nearly precisely normal to the form, this removal process can become much more difficult, since skewed or differently angled rebar will have a greater tendency to resist removal from the form. This will result in increased time and labor spent in "stripping" or removing the forms from the concrete and rebar.
In order to properly position the rebar, the present inventor developed a flexible, annular rubber insert (shown at FIG. 6) which was inserted into spaced holes (e.g., apertures 39 and 50 of FIGS. 1 and 2) associated with the forms. This rubber insert included a recessed ring circumventing the periphery of the insert for engaging the inner surface of the form apertures. The rebar was then placed within the inserts, serving to retain the rebar in place as it was impacted by the concrete mix during pouring. The flexibility of the insert accounted for manufacturing tolerance differences between the rebar and the form apertures, permitting the rebar to be retained in position normal to the form. The use of this insert was a significant improvement over the prior art, since rebar would often be knocked out of position during pouring, decreasing the overall resistance of the concrete to cracking and increasing the difficulty involved in stripping the form.
Despite the advantages these rubber inserts provided over prior art methods of retaining rebar within concrete, there were still disadvantages associated with them. For example, these types of rubber inserts proved to be relatively expensive. This is an important consideration, since in large-scale paving operations thousands of these inserts can be used, and the cost of the rubber inserts tended to require that they be recovered and reused. Further, there were difficulties involved in removing these rubber inserts from the forms. Thus, it was time consuming to individually remove each rubber insert from the forms. A relatively inexpensive rebar retention device which allows the rebar to be properly positioned while facilitating the process of stripping the forms from the concrete and rebar is needed.